Optical filter

ABSTRACT

Polyol(allyl carbonate) monomer, e.g., diethylene glycol bis(allyl carbonate), containing 1,4-dihydroxy anthraquinone in amounts sufficient to selectively absorb at least 94 percent of the visible and ultraviolet light segments of the electromagnetic spectrum below 530 nanometers is described. Also described are ophthalmic articles prepared by curing the monomer.

This is a division of application Ser. No. 617,425, filed June 5, 1984,now U.S. Pat. No. 4,650,605.

DESCRIPTION OF THE INVENTION

Ophthalmic lenses typically transmit high levels of ultravioletradiation. Recently, concern has been expressed that ultravioletradiation may be potentially harmful to the eye. In addition, there aremany individuals who are particularly sensitive to radiation in thelower portion of the visible spectrum, e.g., between about 400 and 550nanometers as a result of ocular conditions such as cataracts.

The use of chemical additives as internal filters for ophthalmic plasticlenses poses several difficulties. Firstly, the chemical additive mustbe soluble in the organic monomer used to produce the solid plasticlens. Secondly, since polymerization of the organic monomer is initiatedby free-radical initiators, e.g., peroxide initiators, the additive mustbe resistant to oxidation caused by the peroxide initiator duringpolymerization. Thirdly, the additive must also be resistant to thermaldegradation brought about by the elevated temperatures used duringpolymerization. Finally, the chemical additive must not adversely affectthe polymerization process, in a significant way, i.e., severely inhibitthe cure or castability of the monomer, or adversely affect the physicalproperties, e.g., the hardness, refractive index, clarity, etc. of thepolymerizate.

There has, therefore, been a continuing search for organic chemicaladditives that are soluble in the organic monomer used to produce theplastic ophthalmic article, are stable to peroxide initiators andthermal degradation, do not adversely affect the physical properties ofthe cured plastic article and which impart to the cured plastic articlethe property of selectively absorbing ultraviolet light and visiblelight in the lower portion of the visible region of the electromagneticspectrum, e.g., up to about 530 or 550 nanometers.

It has now been discovered that polymerizates of polyol(allyl carbonate)monomers that contain an effective amount of 1,4-dihydroxy anthraquinoneselectively absorb at least 94 percent of the ultraviolet and visiblelight segments of the electromagnetic spectrum below the wavelength of530 nanometers. More particularly, it has been discovered thatpoly[polyol(allyl carbonate)], e.g., diethylene glycol bis(allylcarbonate), that contains from above 0.05 to about 0.40 weight percentof 1, 4-dihydroxy anthraquinone selectively absorbs that portion of theelectromagnetic spectrum through 530 nanometers, which includes thepotentially harmful ultraviolet light portion of the electromagneticspectrum and the lower portion of the visible light spectrum, e.g., theblue segment, which are believed to be the primary causes of discomfortfor individuals with ocular conditions, such as that previouslydescribed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood by reference to theattached drawings wherein:

FIG. 1 is a plot of the percent light transmittance against wavelengthfor the electromagnetic spectrum from about 260 to 600 nanometers forpoly[diethylene glycol bis(allyl carbonate)] containing no organic lightfiltering additive; and

FIGS. 2, 3, 4 and 5 are plots of the percent light transmittance againstwavelength for the electromagnetic spectrum from about 400 to 700nanometers for poly[diethylene glycol bis(allyl carbonate)] containingabout 0.20, 0.15, 0.10, and 0.05 weight percent respectively of1,4-dihydroxy anthraquinone.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, there is provided an opticalfilter of poly[polyol(allyl carbonate)] that is capable of selectivelyabsorbing at least 94 percent of the ultraviolet and visible lightsegments of the electromagnetic spectrum below the wavelength of 530nanometers. The aforesaid optical filter is obtained by dissolving inthe liquid polyol(allyl carbonate) monomer an effective amount of1,4-dihydroxy anthraquinone additive and polymerizing the resultingsolution.

1,4-dihydroxy anthraquinone is available commercially. It is oftenreferred to by its classical name, quinizarin, and is listed in theColour Index, Volume 4, page 4515, third edition (1971) as number 58050smoke dye (orange). U.S. Pat. No. 1,886,237 describes the preparation of1,4-dihydroxy anthraquinone by the condensation of 4-chlorophenol withphthalic anhydride in the presence of anhydrous aluminum chloride. Thecomposite product produced by the condensation reaction is subjected toring closure and hydrolysis to produce the desired dihydroxy product.U.S. Pat. No. 2,003,859 describes the condensation of phthalic anhydrideand p-chlorophenol in concentrated sulfuric acid in the presence ofboric acid to produce quinizarin. The Colour Index refers to three othermethods for producing 1,4-dihydroxy anthraquinone among which is thetreatment of anthraquinone with sulfuric acid in the presence of boricacid.

The amount of 1,4-dihydroxy anthraquinone added to the polymerizablepolyol(allyl carbonate) liquid monomer is an effective amount, i.e., anamount such that the resulting polymerizate will absorb at least 94percent of the ultraviolet and visible light spectrum through 530nanometers. Typically, from above 0.05 to about 0.30 or 0.40 weightpercent of 1,4-dihydroxy anthraquinone will be sufficient to provide theabove-described light filtering characteristic. More typically fromabove 0.05, e.g., 0.075, to about 0.20 or 0.25 weight percent of the1,4dihydroxy anthraquinone is used. When used in the aforesaid typicalamounts, at least 94, preferably 95 or 96, percent of ultraviolet andvisible light through 530 nanometers are selectively absorbed by a 2.2millimeter thick polymerizate.

The exact amount of 1,4-dihydroxy anthraquinone required to provide apolymerizate that absorbs a prescribed level of the ultraviolet andvisible light spectrum through 530 nanometers, e.g., 95 percent, willdepend on the thickness of the polymerizate. The thicker thepolymerizate, the less 1,4-dihydroxyanthraquinone required to obtain thedesired percent of light absorption and vice versa. Thus, theconcentration of 1,4-dihydroxy anthraquinone can be varied within theaforedescribed range in order to obtain a level of light absorptionwithin the range of 94-100 percent for light less than 530 nanometersfor a polymerizate of a particular thickness.

Polyol (allyl carbonate) monomers which may be utilized in the practiceof the present invention are the allyl carbonates of linear or branchedaliphatic or aromatic liquid polyols, e.g., aliphatic glycol bis(allylcarbonate) compounds, or alkylidene bisphenol bis(allyl carbonate)compounds. These monomers can be described as unsaturated polycarbonatesof polyols, e.g., glycols. The monomers can be prepared by procedureswell known in the art, e.g., U.S. Pat. Nos. 2,370,567 and 2,403,113. Inthe latter patent, the monomers are prepared by treating the polyol,e.g., glycol, with phosgene at temperatures between 0° C. and 20° C. toform the corresponding polychloroformate, e.g., dichloroformate. Thepolychloroformate is then reacted with an unsaturated alcohol in thepresence of a suitable acid acceptor, e.g., pyridine, a tertiary amine,or an alkali or alkaline earth metal hydroxide. Alternatively, theunsaturated alcohol can be reacted with phosgene and the resultingchloroformate reacted with the polyol in the presence of an alkalinereagent, as described in U.S. Pat. No. 2,370,567.

The polyol (allyl carbonate) monomers can be represented by the graphicformula: ##STR1## wherein R₁ is the radical derived from the unsaturatedalcohol and is an allyl or substituted allyl group, R is the radicalderived from the polyol and n is a whole number from 2 to 5, preferably2. The allyl group (R₁) can be substituted at the 2 position with ahalogen, most notably chlorine or bromine, or an alkyl group containingfrom 1 to 4 carbon atoms, generally a methyl or ethyl group. The R₁radical can be represented by the graphic formula: ##STR2## whereinR_(o) is hydrogen, halogen, or a C₁ -C₄ alkyl group. Specific examplesof R₁ include the groups: allyl, 2-chloroallyl, 2-bromoallyl,2-fluoroallyl, 2-methallyl, 2-ethylallyl, 2-isopropylallyl,2-n-propylallyl, and 2-n-butylallyl. Most commonly R₁ is the allylgroup, H₂ C =CH--CH₂ --.

R₂ is a polyvalent radical derived from the polyol, which can be analiphatic or aromatic polyol that contains 2, 3, 4, or 5 hydroxy groups.Typically, the polyol contains 2 hydroxy groups, i.e., a glycol or abisphenol. The aliphatic polyol can be linear or branched and containfrom 2 to 10 carbon atoms. Commonly, the aliphatic polyol is an alkyleneglycol having from 2 to 4 carbon atoms or a poly(C₂ -C₄) alkyleneglycol, i.e., ethylene glycol, propylene glycol, trimethylene glycol,tetramethylene glycol, or diethylene glycol, triethylene glycol, etc.

The aromatic polyol can be represented by the graphic formula: ##STR3##wherein A is a divalent alkyl radical, e.g., an alkylidene radical,having from 1 to 4 carbon atoms, e.g., methylene, ethylidene,dimethylmethylene (isopropylidene), Ra represents lower alkylsubstituents of from 1 to 3 carbon atoms, and p is 0, 1, 2, or 3.Preferably, the hydroxyl group is in the ortho or para position.

Specific examples of the radical R₂ include: alkylene groups containingfrom 2 to 10 carbon atoms such as ethylene, (--CH₂ --CH₂ --),trimethylene, methylethylene, tetramethylene, ethylethylene,pentamethylene, hexamethylene, 2-methylhexamethylene, octamethylene, anddecamethylene; alkylene ether groups such as --CH₂ --O--CH₂ --, --CH₂CH₂ --O--CH₂ CH₂ --, --CH₂ --O--CH₂ --CH₂ --, and --CH₂ CH₂ CH₂ --O--CH₂CH₂ CH₂ --; alkylene polyether groups such as --CH₂ CH₂ --O--CH₂ CH₂--O--CH₂ CH₂ -- and --CH₂ CH₂ CH₂ --O--CH₂ CH₂ CH₂ --O--CH₂ CH₂ CH₂ --;alkylene carbonate and alkylene ether carbonate groups such as --CH₂ CH₂--O--CO--O--CH₂ CH₂ --and --CH₂ CH₂ --O--CH₂ CH₂ --O--CO--O--CH₂ CH₂ --;and isopropylidene bis(paraphenyl), ##STR4## Most commonly, R₂ is --CH₂CH₂ --, --CH₂ CH₂ --O--CH₂ CH₂ --, or --CH₂ CH₂ --O--CH₂ CH₂ --O--CH₂CH₂ --.

Preferred are the bis(allyl carbonate) monomers which can be representedby the graphic formula: ##STR5## wherein R₁ and R₂ are as defined above.

Specific examples of polyol(allyl carbonate) monomers useful in thepractice of the invention herein contemplated include ethylene glycolbis(2-chloroallyl carbonate), ethylene glycol bis(allyl carbonate),diethylene glycol bis(2-methallyl carbonate), diethylene glycolbis(allyl carbonate), triethylene glycol bis(allyl carbonate), propyleneglycol bis(2-ethylallyl carbonate), 1,3-propanediol bis(allylcarbonate), 1,3butanediol bis(allyl carbonate), 1,4-butanediolbis(2,-bromoallyl carbonate), dipropylene glycol bis(allyl carbonate),trimethylene glycol bis(2-ethylallyl carbonate), pentamethylene glycolbis(allyl carbonate), ns isopropylidene bisphenol bis(allyl carbonate).

Industrially important polyol bis(allyl carbonate) monomers which can beutilized in the invention herein contemplated are: ##STR6## Diethyleneglycol bis(allyl carbonate) is preferred. This monomer is commerciallyavailable from PPG Industries, Inc. and is sold under the trademarkCR-39 Allyl Diglycol Carbonate.

Because of the process by which the polyol(allyl carbonate) monomer isprepared, i.e., by phosgenation of the polyol (or allyl alcohol) andsubsequent esterification by the allyl alcohol (or polyol), the monomerproduct can contain related monomer species in which the moietyconnecting the allyl carbonate groups contains one or more carbonategroups. When the polyol is a diol, these related monomer species can berepresented by the graphic formula: ##STR7## wherein R₁ is as definedabove with respect to graphic formula I, R₃ is a divalent radical, e.g.,alkylene or phenylene, derived from the diol, and s is a whole numberfrom 2 to 5. The related monomer species of diethylene glycol bis(allylcarbonate) can be represented by the graphic formula, ##STR8## wherein sis a whole number from 2 to 5. The polyol(allyl carbonate) monomer cantypically contain from 2 to 20 weight percent of the related monomerspecies and such related monomer species can be present as mixtures,i.e., mixtures of the species represented by s being equal to 2 3, 4etc.

In addition, a partially polymerized form of the polyol(allyl carbonate)monomer can be used. In that embodiment, the monomer is partiallypolymerized by using small, e.g., 0.5-1.5 phm, amounts of initiator orthickened by heating to provide a non-gel containing, more viscousmonomeric material.

As used in the present description and claims, the term polyol(allylcarbonate) monomer or like names, e.g., diethylene glycol bis(allylcarbonate), are intended to mean and include the named monomer orprepolymer and any related monomer species contained therein.

Other copolymerizable monomeric materials may also be present with thepolyol(allyl carbonate) monomer. For example, a viscosity increasingmonomeric material may be dispersed in the monomer, as described in U.S.Pat. No. 4,346,197. Other materials such as allyl S-triazines andurethanes having acrylate functionality, as described in U.S. Pat. No.4,360,653, may be present in the monomer to modify the ultimate physicaland thermal properties of the polymer. U.S. Pat. No. 4,139,578 describesthe presence of unsaturated polyester and unsaturated copolymerizablemonomer to decrease the shrinkage that occurs during polymerization ofpolyol(allyl carbonate) monomers. Hence, as herein contemplated, thepolyol(allyl carbonate) monomer to be polymerized may also containminor, e.g., less than 50 weight percent, of other copolymerizablematerials which are used to modify the ultimate properties or processingcharacteristics of the polyol(allyl carbonate) monomer.

The polymerizable polyol(allyl carbonate) monomer containing1,4-dihydroxy anthraquinone can be prepared by admixing the twomaterials in a suitable vessel at room temperature. The rate ofdissolution of the 1,4-dihydroxy anthraquinone can be increased byheating the polymerizable monomer, e.g., up to 50-60° C. Alternatively,the 1,4-dihydroxy anthraquinone can be dissolved in the monomer up toits solubility limit to thereby form a concentrate which can then bediluted with the polyol(allyl carbonate) monomer to provide apolymerizable mixture containing the desired amount of 1,4-dihydroxyanthraquinone. For example, a 1.6 percent concentrate of 1,4-dihydroxyanthraquinone in diethylene glycol bis (allyl carbonate) monomer can beprepared by heating the appropriate mixture of the anthraquinone andmonomer to 80-90° C. with agitation. A casting solution containing 0.20weight percent of the anthraquinone can then be prepared by blending 1part of the hot concentrate with 7 parts of monomer.

Polymerization of the 1,4-dihydroxy anthraquinone - containingpolyol(allyl carbonate) polymerizable monomer is effected by adding afree-radical initiator, e.g., a peroxide initiator, to the mixture andheating the mixture. Such organic peroxides are well known in the art.Preferred free-radical initiators are organic peroxy compounds, such asperoxyesters, diacyl peroxides, peroxydicarbonates and mixtures of suchperoxy compounds.

Examples of peroxy compounds include: peroxydicarbonate esters such asdi(n-propyl)-, diisopropyl-, di(n-butyl)-, di(secondary butyl)-,diisobutyl-, di(2-ethylhexyl)-, dicetyl-, dicyclohexyl- anddi(4-tertiarybutyl cyclohexyl) peroxydicarbonate; diacyl peroxides suchas diacetyl-, dibenzoyl-, dilauroyl-, and diisobutyryl peroxide; andperoxyesters such as tertiarybutyl peroxypivalate, tertiarybutylperoctoate and tertiarybutyl perneodecanoate.

The amount of peroxide initiator can vary but generally will be aninitiating amount, i.e., an amount sufficient to produce a fully curedsolid polymerizate utilizing the time period and temperatures of thecure cycle chosen. The amount of peroxide initiator used will typicallyvary from about 2.0-10.0 parts of peroxide per hundred parts of monomer.More typically, from about 3.0 to 5, e.g., 3.5, parts of peroxide perhundred parts of monomer (phm) are used.

The polyol(allyl carbonate) monomer may be polymerized in an air oven orin a water bath. The time of polymerization, or cycle, is a function ofthe rate at which the heat of polymerization can be removed, whichdepends on the thickness of the article to be produced. A completediscussion of the time-temperature relationship for cure cycles ofdiethylene glycol bis(allyl carbonate) can be found in the article,"Polymerization Control In Casting A Thermosetting Resin" by William R.Dial et al, Industrial and Engineering Chemistry, Volume 47, page2447-51, December 1955.

In one exemplification of the present invention, 0.20 weight percent of1,4-dihydroxy anthraquinone is added to diethylene glycol bis(allylcarbonate) and the resulting mixture polymerized by the addition of 3.5weight percent diisopropyl peroxydicarbonate. The resulting polymerizatehas an orange hue, is optically clear and haze free, and absorbs greaterthan 95 percent of all incident light and radiation below 530nanometers, i.e., from 200-530 nanometers.

The present invention is more particularly described in the followingexamples, which are intended as illustrative only since numerousmodifications and variations therein will be apparent to those skilledin the art. In the examples, polymerization products are tested for thefollowing properties using the physical test methods hereinafterdescribed.

1. Light transmission and haze--The percent light transmission andpercent haze are measured using a Hunter lab colorimeter, Model D25P-2;and

2. Barcol hardness--This property is measured in accordance with ASTMTest Method D2583-81 using a Barcol impressor.

EXAMPLE I

Diethylene glycol bis(allyl carbonate) (200 grams) was charged to abeaker and 0.40 grams of 1,4-dihydroxy anthraquinone added to thebeaker. The contents of the beaker were heated to about 50° C. withmixing for about 15-30 minutes to dissolve the anthraquinone additive.The resulting solution was cooled to ambient temperature and thenfiltered through a 5 micron membrane. Diisopropyl peroxydicarbonate(3.50 weight percent) was added to the cooled, filtered solution and themixture injected into a mold formed by two 4 inch×4 inch (10.2×10.2centimeters) glass plates separated by a 2.2 millimeter ethylene vinylacetate gasket. The mold was then heated gradually from about 44° C. to90° C. over a period of 16 1/2 hours. Thereafter, the temperature of themold was increased to 105° C. over 20 minutes and the mold maintained atthat temperature for an additional 10 minutes.

While still hot, the glass plates of the mold were separated. Theresulting polymeric sheet casting was tested for Barcol hardness, hazeand light transmittance. A summary of results are tabulated in Table Iand the portion of the transmission spectra in the range of from about520 to 700 nanometers depicted in FIG. 2.

EXAMPLE II

The procedure of Example I was repeated three times while varying theamount of 1,4-dihydroxy anthraquinone. The amount of 1,4-dihydroxyanthraquinone used was 0.15 weight percent, 0.10 and 0.05 weight percentrespectively in the three-repetitions. The data obtained is tabulated inTable I and the appropriate portion of each of the generatedtransmission spectra from about 200 to 700 nanometers for the resultingpolymerizates is depicted in FIGS. 3, (0.15 wt. %) 4, (0.10 wt. %) and 5(0.05 wt. %).

EXAMPLE III (Comparative)

The procedure of Example I was repeated except that no 1,4-dihydroxyanthraquinone was added to the diethylene glycol bis(allyl carbonate).The data obtained is tabulated in Table I and the portion of thegenerated transmission spectra from about 260 to 600 nanometers depictedin FIG. 1.

                                      TABLE I                                     __________________________________________________________________________                                                Visible       Barcol              1,4-Dihydroxy    Luminous Transmittance, % Wavelength, nm                                                                 (White Light) Hardness            Example                                                                            Anthraquinone, wt. %                                                                      300-400                                                                            401-499                                                                            500                                                                              520                                                                              540                                                                              560                                                                              600-700                                                                            Transmission,                                                                          Haze,                                                                              15                  __________________________________________________________________________                                                              sec.                I    0.20        <1   <1   <1 <1 16 73 90-91                                                                              50.3     1.2  17                  II (a)                                                                             0.15        <1   <1   <1  2 27 77 90-91                                                                              53.3     1.1  20                  II (b)                                                                             0.10        <1   ≦3                                                                           3  10                                                                              52 82 90-91                                                                              59.6     1.3  23                  II (c)                                                                             0.05        <1   ≦30                                                                          30                                                                               45                                                                              73 87 90-91                                                                              73.3     0.8  26                  III  0           ≦91                                                                          91   91                                                                               91                                                                              91 91 92   92.6     0.6  26                  __________________________________________________________________________

The data of Table I and FIGS. 1-5 show that the addition of low levelsof 1,4-dihydroxy anthraquinone has a dramatic effect on the ultravioletand visible transmittance of the cast polymerizate. A 0.20 weightpercent level of that anthraquinone additive effectively absorbsultraviolet and visible radiation between 300 and 520 nanometers. Lowerconcentrations will produce various alterations of the transmissioncurves. A lens prepared from such a polymerizate would protect portionsof the eye from potentially harmful photochemical damage from nearultraviolet and/or blue light. Beyond about 520-530 nanometers, thebegin to transmit some green, yellow, orange, and red light, eventuallyreaching at least 90 percent transmittance at about 600 nanometers.Further, the castings demonstrate good cure and optical properties. Thelevels of haze and Barcol hardness exhibited by the castings are wellwithin acceptable ranges. Finally, the castings exhibit reducedtransmission of visible or white light.

Articles prepared from the compositions of the present invention may beused in those applications which require filtration of light radiationof wave lengths below about 530 nanometers. In particular, polymerizatesof the present invention may be used as ophthalmic lenses forindividuals that are sensitive to visible light and ultraviolet energybelow the wave length of 530 nanometers, or for general sunglassapplications.

Although the present invention has been described with reference tospecific details of certain embodiments thereof, it is not intended thatsuch details should be regarded as limitations upon the scope of theinvention except as and to the extent that they are included in theaccompanying claims.

I claim:
 1. A polyol(allyl carbonate) polymerizate that contains1,4-dihydroxy anthraquinone in amounts such that the polymerizateabsorbs at least 94 percent of the visible and ultraviolet lightsegments of the electromagnetic spectrum below the wavelength of 530nanometers, and that has been prepared by polymerizing a mixture of1,4-dihydroxy anthraquinone and liquid polyol(allyl carbonate) monomer.2. An ophthalmic article of poly[diethylene glycol bis(allyl carbonate)]that contains from above 0.05 to about 0.40 weight percent,1,4-dihydroxy anthraquinone, the anthraquinone being present in amountssuch that the article selectively absorbs at least 94 percent of thevisible and ultraviolet light segments of the electromagnetic spectrumbelow the wavelength of 530 nanometers, and that has been prepared bypolymerizing a mixture of 1,4-dihydroxy anthraquinone and liquidpoly[diethylene glycol bis(allyl carbonate)].
 3. The polymerizate ofclaim 1 wherein the anthraquinone is present in amounts of from above0.05 to about 0.40 weight percent.
 4. The polymerizate of claim 3wherein the polyol(allyl carbonate) is represented by the followinggraphic formula, ##STR9## wherein R₂ is an alkylene glycol having from 2to 4 carbon atoms or a poly(C₂ -C₄) alkylene glycol, and R₁ is the allylradical, ##STR10## wherein R_(o) is hydrogen, halogen or a C₁ -C₄ alkyl5. The polymerizate of claim 4 wherein the polyol(ally carbonate) isdiethylene glycol bis(allyl carbonate).
 6. The article of claim 2wherein the article is an ophthalmic lens.
 7. The article of claim 2wherein the article contains from about 0.075 to about 0.25 weightpercent of 1,4-dihydroxy anthraquinone.